The researchers looked at two types of stars Cryptasperina pentagona and C. hystera, living on the Australian coast.

Both have dramatically different sex lives, said Science Daily, with one having male and female species that breed small stars in plankton, while the other species is a hermaphrodite that breed their young inside and give birth to mini stars.

Looking at their DNA sequences, scientists were able to determine when the two species diverged.

The period between their split and the evolution of their diferences is considered dramatic.

"It's as dramatic a difference in life history as in any group of organisms," said Grosberg.